When fabricating integrated circuits, a plurality of films are deposited onto a wafer. These films are selectively patterned, etched, doped, reacted, etc. to provide the desired functions for electronic devices. The patterning process can use a variety of well-known pattern transfer methods (e.g., using a pattern mask to transfer an image to the deposit film). After the deposited film is covered with a patterned mask, such as a photoresist layer, the exposed portion of the deposited film can then be removed.
Etching processes are used extensively in semiconductor manufacturing to remove exposed portions of the deposited film. One etching process that can be used to remove the exposed film is dry, or RF-plasma assisted, etching which uses plasma in the form of a low pressure gaseous discharge. This etching process provides a high fidelity transfer of resist patterns.
In some instance, etchant species are activated outside of the process chamber where the deposited film may potentially be damaged by plasma generated within the process chamber. When this excitation is provided outside of the process chamber, the process may be referred to as either after-glow, downstream or remote plasma etching. If additional excitation is required, it can be accomplished in the process chamber.
Defects are caused by the presence of particulates on a surface of the process materials. This is one of the reasons for the switch from wet etches to dry etches. Under certain conditions, however, remote plasma-etching can create particulates that are generated and carried to the surface of the etchant stream, thereby contaminating the surface of the process material.
One variety of remote plasma-etching activates the etchant by passing it through a microwave cavity. The process gases, including the etchant, flow through a discharge tube formed from a relatively inert insulating material (e.g., quartz) which passed through a microwave cavity. These activated process gases, in combination with high temperatures, can etch the internal surfaces of the quartz discharge tube, creating quartz particulates. Unfortunately, these generated quartz particulates are passed through process stream, to the face of the surface, and inevitably cause contamination to the surface of the semiconductor material.
Thus, there is a need for a remote plasma-etching process which does not contaminate the surface being processed. Consequently, it is desirable to activate the etchant, as close as possible to the surface of the wafer being etched, to eliminate any contamination caused when passing the activated gas through the quartz tubes of the process. Additionally, increased selectivity of activating the etchant would increase the control over the etching of the semiconductor materials.